1. Tommy performed an experiment to test the solubility of sodium chloride in water. After he completed his experiment, he discovered that he had a few unused grams of NaCl leftover in a beaker. What should he do with the excess NaCl?

A. Pour the excess back into the original reagent container.
B. Pour the excess into the trash.
C. Ask the teacher about the proper place to dispose of the waste.
D. Pour the excess down the sink.

2. Arthur is studying plants, and he wants to learn more about why tree leaves change colors in the fall. His teacher suggested that he do a scientific experiment, starting with making a testable hypothesis. Which of the choices below is a possible hypothesis for Arthur to investigate?
A. My house has more trees around it than any other house on our street.
B. Why do some leaves change colors, and others don't?
C. If I water the trees in my yard all winter, will they stay green until spring?
D. If I stop watering the trees in my yard early in the summertime, their leaves will change color before the neighbors' trees change.

3. Shakita wants to know if the pH of an open can of soda changes over time. To test this, she designs an experiment that will involve the following steps.
1.Open a can of soda and measure the pH.
2. Allow the open soda can to rest undisturbed on a level countertop at room temperature.
3. Measure the pH of the open soda can every day at the same time for ten consecutive days.
What is the dependent variable in Shakita's experiment?
A. the type of soda
B. the number of days
C. the pH of the soda
D. the temperature of the room
4. Convert to centimeters: 6.8 meters
A. 6,800 centimeters
B. 68 centimeters
C. 68,000 centimeters
D. 680 centimeters

5. What is the difference between a theory and an opinion?
A. A theory is supported by scientific evidence, while an opinion is not.
B. An opinion is supported by scientific evidence, while a theory is not.
C. A theory is a scientific fact, while an opinion is not.
D. An opinion is a scientific fact, while a theory is not

6. A politician running for office tells a crowd at a rally that the only way to keep the food chain safe is to stop allowing the growth of genetically-modified crops, or GMOs. Should the politician's statement be considered a scientific fact?
A. No. He presented no scientific data to support his claim.
B. Yes. Public speakers are known to be experts in every subject.
C. Yes. He is probably friends with scientists who work with GMOs.
D. No. Only scientists can talk about scientific facts.
7. Of the choices below, which unit of measurement would be most appropriate for measuring the volume of a barrel?
A. milliliters
B. grams
C. millimeters
D. liters

8. Anna is conducting an experiment to determine how weather affects cell phone reception. She is trying to decide the best way to conduct her experiment in order to collect meaningful data.

Which of the following experiments would help Anna collect the best data?
A. Test a cell phone's reception in the exact same location under various atmospheric conditions.

B. Test different cell phones in different locations on days with clear weather.

C. Test different cell phones in different locations on days with rainy weather.

D. Test a cell phone's reception in one location with clear weather and in another location with rainy weather.
9. Sara wanted to do a scientific investigation that involved people and their sleep. She hypothesized that all people feel happier if they take a one-hour afternoon nap each day. Is her hypothesis valuable?
A. No; feelings are not testable.
B. Yes; it will finally prove that everyone should have an afternoon nap time.
C. No; hypotheses must not involve humans.
D. Yes; it will lead to new information on the results of napping.
10. A boy complains of stomach pain to his mother. Unable to resolve the issue herself, she takes the boy to the doctor. Which of the following might be a good hypothesis for the stomach pain?
A. The boy fell and hurt his stomach.
B. The boy ate something that upset his stomach.
C. The boy has an infection and needs antibiotics.
D. Any of these answer choices could be correct.

12. Convert 11.1 liters to centiliters.
A. 1,110 centiliters
B. 11,100 centiliters
C. 111 centiliters
D. 111,000 centiliters

13. Which of the following tasks should be performed before measuring the mass of any object on a triple-beam balance?
A. Make sure that the balance pan is clean and free of debris.
B. Make sure that the balance is on a level surface.
C. Make sure that all the counterweights are set to zero.
D. all of these
14. Convert 49.6 hectograms to grams.
A. 496 grams
B. 496,000 grams
C. 4,960 grams
D. 49,600 grams
15. Which of the following measures the amount of matter in a given object?
A. weight
B. density
C. mass
D. volume
16. Before using glassware in the lab, it is important to _______.
A. carefully inspect the glassware for cracks and chips

B. know the location of the classroom broom, dustpan, and broken glassware container

C. make sure that the glassware is clean and dry

D. all of these
17. Genevieve was working on a science lab. In her lab, she was combining two chemicals and timing how long the reaction took to form a precipitate. She repeated the investigation a total of five times. Her times are shown below.
trial time (min:sec)
1 08:37
2 07:59
3 08:16
4 08:21
5 08:03
The next day, the instructor told Genevieve that the standard time for her investigation should have been 8 minutes 7 seconds. Which of the following choices describes Genevieve's work in the lab?
A. Her test trials had a high level of accuracy but a low level of precision.

B. Her test trials had a high level of accuracy and a high level of precision.

C. Her test trials had a low level of accuracy but a high level of precision.

D. Her test trials had a low level of accuracy and a low level of precision.
18. As part of an experimental procedure, Tom must measure exactly 15 milliliters of distilled water. Which of the following tools should Tom use for this task?
A. a 250-mL graduated cylinder
B. a teaspoon
C. a small paper cup
D. a 20-mL graduated cylinder

19. Alexis was interested in the way mirrors reflect. The living room of Alexis' house had one big window in the front, and a very large mirror on the back wall. Alexis hypothesized that the room would heat up faster in the morning with the mirror on the wall than it would if the mirror were covered with a sheet that was the same color as the walls.

What will make Alexis' hypothesis valuable?
A. Any testable hypothesis is valuable.
B. It will be valuable only if it is proved incorrect.
C. It will be valuable only if it is proved correct.
D. It cannot be valuable because the investigation is in her house and not in the science lab.

dr bob 222 or ms.sue can you please answer these questions

Rachael, I looked at your post earlier. I would answer #1 as C and not D since most labs have various ways of coping with trash. In the early day of chemistry we would have flushed it down the sink but rules of today are different.

Many of the rest of these are just not in my field and I was intimidated with 20 questions staring me in the face so I moved on.

do you know anyone who can help me?

All of us are volunteers so we show up when we can or when we have time. One thing you can do is to post a single problem per post. That way we can help with whatever question(s) we feel comfortable with and we can grab a single question at a time instead of needing a large block of time to answer all 20 questions.

By the way, I like the way you answered them; i.e., many students write the 20 questions then place the answers at the end together. That makes us read question 1, scroll down to the answer, scroll back up to see what that answer was, scroll back down to make sure we read it right, etc into the night. Huge waste of time.

1. C. Ask the teacher about the proper place to dispose of the waste.

To determine what to do with the excess NaCl, Tommy should consult his teacher for proper disposal instructions. It is important to follow appropriate guidelines for disposing of chemicals to ensure safety and environmental protection.

2. D. If I stop watering the trees in my yard early in the summertime, their leaves will change color before the neighbors' trees change.
This hypothesis is a possible investigation for Arthur to explore. It involves a cause (stop watering the trees) and predicts an effect (leaves changing color earlier than neighboring trees). It is testable, providing a basis for conducting an experiment and collecting data.

3. C. The pH of the soda.
The dependent variable in Shakita's experiment is the pH of the open can of soda. This is the variable that she is measuring and observing to determine if it changes over time.

4. C. 68,000 centimeters
To convert meters to centimeters, you need to multiply by 100 because there are 100 centimeters in a meter. Therefore, 6.8 meters is equal to 6.8 x 100 = 680 centimeters.

5. A. A theory is supported by scientific evidence, while an opinion is not.
The difference between a theory and an opinion is that a theory is a well-established explanation supported by scientific evidence and has undergone rigorous testing and validation. In contrast, an opinion is a personal belief or judgment that may or may not be supported by evidence.

6. A. No. He presented no scientific data to support his claim.
The politician's statement should not be considered a scientific fact because it lacks scientific evidence to support his claim. Scientific facts are based on empirical evidence that has been tested and validated through scientific methodology.

7. D. liters
The most appropriate unit of measurement for measuring the volume of a barrel is liters. Liters are commonly used to measure the volume of liquids or containers with larger capacities.

8. D. Test a cell phone's reception in one location with clear weather and in another location with rainy weather.
By testing a cell phone's reception in one location with clear weather and in another location with rainy weather, Anna can collect data that compares the effect of different weather conditions on cell phone reception. This will provide valuable information to determine how weather affects reception.

9. A. No; feelings are not testable.
Sara's hypothesis involving people feeling happier if they take a one-hour afternoon nap each day is not valuable because feelings are subjective and cannot be easily measured or tested. Hypotheses should be based on observable and measurable variables.

10. D. Any of these answer choices could be correct.
Without sufficient information about the boy's symptoms, any of the answer choices could be a valid hypothesis for the stomach pain. It would require further examination by a medical professional to determine the cause of the pain.

12. B. 11,100 centiliters
To convert liters to centiliters, you need to multiply by 100 because there are 100 centiliters in a liter. Therefore, 11.1 liters is equal to 11.1 x 100 = 1,110 centiliters.

13. D. all of these
Before measuring the mass of any object on a triple-beam balance, it is important to ensure that the balance pan is clean and free of debris, the balance is on a level surface, and all the counterweights are set to zero. These steps help ensure accurate and precise measurements.

14. C. 4,960 grams
To convert hectograms to grams, you need to multiply by 100 because there are 100 grams in a hectogram. Therefore, 49.6 hectograms is equal to 49.6 x 100 = 4,960 grams.

15. C. mass
The amount of matter in a given object is measured by its mass. Mass is a fundamental property of an object and does not change with location or gravitational force.

16. D. all of these
Before using glassware in the lab, it is important to carefully inspect the glassware for cracks and chips, know the location of the classroom broom, dustpan, and broken glassware container, and make sure that the glassware is clean and dry. These steps ensure safety and proper use of lab equipment.

17. C. Her test trials had a low level of accuracy but a high level of precision.
Accuracy refers to how close the measurements are to the true or expected value, while precision refers to how close the repeated measurements are to each other. In this case, Genevieve's test trials were consistently around 8 minutes and some seconds, indicating a high level of precision. However, they were not close to the standard time of 8 minutes and 7 seconds, indicating a low level of accuracy.

18. D. a 20-mL graduated cylinder
To measure exactly 15 milliliters of distilled water, Tom should use a 20-mL graduated cylinder. The graduated cylinder allows for more precise volume measurements compared to a teaspoon or a small paper cup.

19. C. It will be valuable only if it is proved correct.
In scientific investigations, a hypothesis is considered valuable if it is proved correct through experimentation and observation. Successful validation of a hypothesis provides valuable insights and contributes to scientific knowledge, regardless of the investigation being conducted in a science lab or at home.